1. Field of the Invention
The present invention relates in general to a fuel pumping unit for pumping gasoline or other liquid fuel from a fuel tank to an engine, and particularly to such a unit which minimizes the production of fuel vapors in a fuel tank.
2. Description of Prior Developments
In some engine fuel supply systems, the fuel pump is located in a reservoir within the main fuel tank. The reservoir contains a reserve supply of fuel that is available to the pump when the tank runs out of fuel, or when the fuel in the tank sloshes back and forth so as to be momentarily out of contact with the pump inlet.
The location of the pump and reservoir in the fuel tank can bring about some problems. For example, servicing the pump within the tank is relatively difficult and time consuming. Also, it is difficult to mount a standard fuel pumping unit in a range of differently sized fuel tanks. Each installation has to be tailored to fit a particular fuel pumping system to a given size fuel tank.
Fuel supply systems for engines equipped with fuel injectors are designed to supply excess quantities of pressurized fuel to the injectors. Fuel not used by the injectors is ordinarily returned to the fuel tank for assimilation back into the fuel supply.
During its passage through the fuel injector system, the unused fuel is generally heated by contact with heated engine surfaces, so that the fuel returned from the engine to the fuel tank is in a heated condition. In conventional arrangements, the heated fuel mixes with the fuel in the tank thereby raising the temperature level in the tank fuel. This is disadvantageous in that the relatively high temperature levels can generate excess fuel vapor which poses a potential air pollution problem.